Proceedings of a symposium sponsored by · 629 JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd21 December 2015 11:51 AM 629 SPECIATION AND CHARACTERIZATION OF

JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd iii 21 December 2015 11:51 AM

Proceedings of a symposium sponsored bythe Materials Characterization Committee of

the Extraction and Processing Division of The Minerals, Metals & Materials Society (TMS)

held during

Edited by:

Shadia Jamil Ikhmayies, Bowen Li, John S. Carpenter, Jiann-Yang Hwang, Sergio Neves Monteiro, Jian Li,

Donato Firrao, Mingming Zhang, Zhiwei Peng, Juan P. Escobedo-Diaz, and Chenguang Bai

FEBRUARY 14-18 DOWNTOWN NASHVILLE, TENNESSEE MUSIC CITY CENTER

JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd iv 21 December 2015 11:51 AM

Copyright © 2016 by The Minerals, Metals & Materials Society. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of The Minerals, Metals, & Materials Society, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of mer-chantability or fitness for a particular purpose. No warranty may be created or extended by sales rep-resentatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

Wiley also publishes books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit the web site at www.wiley.com. For general information on other Wiley products and services or for technical sup-port, please contact the Wiley Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.

Library of Congress Cataloging-in-Publication Data is available.

ISBN 978-1-119-26439-2

Printed in the United States of America.

10 9 8 7 6 5 4 3 2 1

xiii

JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd xiii 21 December 2015 2:25 PM

Brillouin Scattering Spectroscopy on Mg-Nd Alloy in Different Aging Time ...........577Xinyi He, Wenjian Meng, and Yongquan Wu

The Characterization of the Desulfurization Powder in the Semi-Dry De-SO2 Process of the Sintering Plant Exhaust Gas and Its Interaction with the Soil Particles ..........................................................................................585

Ling-Chen Kang, Li-jun Lu, Gai-feng Xue, and Jiann-Yang Hwang

Direct Synthesis of Carbon Nanotubes at Low Temperature by the Reaction of CCl4 and Ferrocene ..........................................................................593

Wei Luo, Yan Tang, Mingsheng He, Degang Ouyang, Cuijiao Ding, Bin Han, Shanhe Zhu, and Minghui Li

Effect of Magnesium Aluminate Spinel Content on Properties of BN Based Composites .........................................................................................599

Meng Liu, Yijie Song, Xiaohong Xu, Guotao Xu, Gaifeng Xue, and Jixiong Liu

Silver Cementation with Zinc from Residual X Ray Fixer, Experimental and Thermochemical Study .................................................................................605

M. Pérez Labra, M. Reyes Pérez, J.A. Romero Serrano, E.O. Ávila Dávila, F.R. Barrientos Hernández, and Pandiyan Thangarasu

Characterization of Waste Molding Sands, for Their Possible Use as Building Material .................................................................................................615

Mauricio Guerrero R., Juan Hernández A., Javier Flores B., Eleazar Salinas R., Isauro Rivera L., Ma. Isabel Reyes V., Eduardo Cerecedo S., Víctor E. Reyes C., and Carmen Cortés L.

Improvement of Mechanical Properties in Natural Rubber with Organic Fillers ......623M. Gonzales-Fernandes, C.G. Bastos Andrade, F.J. Esper, F.R. Valenzuela-Diaz, and H. Wiebeck

Speciation and Characterization of E-Waste, Using Analytical Techniques ........629C. Cortés López, V.E. Reyes Cruz, M.A. Veloz Rodríguez, J. Hernández Ávila, J. Flores Badillo, and J.A. Cobos Murcia

Development of Bio-Based Foams Prepared from PBAT/PLA Reinforced with Bio-Calcium Carbonate Compatibilized by Electron-Beam Radiation .......637

Elizabeth Carvalho L. Cardoso, Marcus Vinicius S. Seixas, Helio Wiebeck, René R. Oliveira, Glauson Aparecido F. Machado, and Esperidiana A.B. Moura

363

JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd 363 21 December 2015 11:51 AM

Soft Materials

Session Chairs:Sergio Monteiro

Zhiwei Peng

Characterization of Minerals, Metals, and Materials 2016

425


Electronic, Magnetic, Environmental, and Advanced Materials

Session Chairs:Shadia Jamil Ikhmayies

Eren Yunus Kalay


483


Poster Session


629


SPECIATION AND CHARACTERIZATION OF E-WASTE, USING ANALYTICAL TECHNIQUES

C. Cortés López 1, V. E. Reyes Cruz1, M. A. Veloz Rodríguez1, J. Hernández Ávila1,

J. Flores Badillo1, J.A. Cobos Murcia1, 2

1 Universidad Autónoma del Estado de Hidalgo, Área Académica de Ciencias de la Tierra y Materiales, Carr. Pachuca-Tulancingo km 4.5 C.P.42184

2Consejo Nacional de Ciencia y Tecnología, Depto. de Cátedras, Av. Insurgentes Sur 1582, Col. Crédito Constructor, Delegación Benito Juárez, México D.F., C.P. 03940.

Abstract Electronic waste (e-waste), have a high potential as a source of precious metals, since they can contain metals like silver, gold, platinum, copper, zinc, nickel, tin and others. In this paper some e-waste were characterized using several analytical techniques as Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and inductively coupled plasma (ICP) in addition to the thermodynamic study by Pourbaix diagrams of silver (Ag), gold (Au), platinum (Pt), copper (Cu), nickel (Ni), tin (Sn) and zinc (Zn); considering an average low concentration of HNO3 (10% v/v). With results of the characterization was determined that the e-waste is an ideal source for the recovery of valuable metals. Similarly, the thermodynamic studies showed that it is possible to obtain all metallic species except Pt, in a potential window of 1.45V to 2.0V vs SCE. Keywords: e-waste, Pourbaix, thermodynamic, x-ray diffraction, electron microscopy.

Introduction Metals in the electronic industry are intended to be used for connecting cables, soldering, printed circuit boards, switches and touch screens. Among the most commonly used metals are copper, barium, nickel, zinc, tantalum, iridium, vanadium, silver, gold, beryllium, manganese, antimony, bismuth, mercury and selenium. This is due to its conductive and corrosion resistance characteristics. The metals contained in electronic waste (e-waste) make them a potential source for the recovery of high economic value metals such as: Ag, Au, Pt, Cu, Ni, Zn and Sn. The lack of technologies for a selective recovery in many countries, have promoted the illegal removal of these residues. In this paper, trying to contribute to the development of some alternatives, a general view is established for the electrochemical leaching of Ag, Au, Pt, Cu, Ni, Zn and Sn, derived from e-waste. First, a characterization study by SEM-EDS, XRD and ICP techniques, is performed. Then, Pourbaix diagrams of Ag, Au, Pt, Cu, Ni, Zn and Sn were constructed considering a low concentration electrolyte of HNO3 (10% v/v).

Characterization of Minerals, Metals, and Materials 2016Edited by: Shadia Jamil Ikhmayies, Bowen Li, John S. Carpenter, Jiann-Yang Hwang, Sergio Neves Monteiro, Jian Li,

Donato Firrao, Mingming Zhang, Zhiwei Peng, Juan P. Escobedo-Diaz, and Chenguang BaiTMS (The Minerals, Metals & Materials Society), 2016

630


Experimental Sample characterization The Characterization of the metal sample material of e-waste that was provided by the company “Corporación de Valores Reciclados SA de C.V.”, was performed by the SEM-EDS, XRD and ICP techniques to determine the content values of the metals (Ag, Au, Pt, Cu, Ni, Zn and Sn). The SEM-EDS characterization of the metal powder from the e-waste was carried out using an electronic microscope JEOL JSM-6300, with high vacuum, energy dispersive MORAN detector and using a magnification of 20X, with a 20kV acceleration voltage. In addition, the EDS analysis was made using different regions of the e-waste sample, to obtain an average concentration. The XRD analysis of the e-waste sample was performed using a NEM Equinox 2000 diffractometer, with a cobalt Co-K 1 source at 20 kV and 30 mA. A spectrophotometer Perkin Elmer Optima 8300 was used for the study of e-waste sample by ICP. 1g of the sample was digested using concentrated HCl and HNO3 2: 1 and heating for 15 min. Thermodynamic study For the Pourbaix diagrams construction of the Ag, Au, Pt, Cu, Ni, Zn and Sn species the free software HSC Chemistry 5 was used. Simulation was performed considering a nitric acid concentration of 10% v/v (2.4 M), at room temperature and the Ag, Au, Pt, Cu, Ni, Zn and Sn concentrations of 9.1x10-5M, 4.2 x10-5M, 4.1 x10-6M, 2.88 x10-M, 2.86 x10-3M, 2.4 x10-3M, 8.39 x10-4M , obtained by ICP, respectively.

Results Sample characterization Figure 1 shows a micrograph from the e-waste powder sample with a 20X magnification. It can be observed a regular morphology of the metallic particles and a size nearby to 1 mm and white areas, which are due to the presence of plastic components from the electronic circuitry of the e-waste.

Figure 1 E-waste powder micrograph at 20X using 20 kV.

631


Table 1 shows the results of average weight percentages of the metals contained in the two regions under study of the sample obtained by EDS analysis.

Table 1 Percentages of the metals found in e-waste powder by SEM-EDS

Element average weight / % Cu Ni Zn Ag Au Sn Pt

58.4 ± 2.1 25.0 ± 2.8

0 0.04 ± 0.06 10.01 ± 0.1

6.6 ± 4.8 0

This table shows that the most economically valuable metals, Au and Ag, have 10.01% and 0.04% weight percentage respectively. Also it is observed that the metals with the highest concentration are Cu with a concentration of 58.4 % and Ni with 25.0%. It is noteworthy to point out that the SEM-EDS technique is semi-quantitative, so it is not possible to properly ascertain the content of Ag and Pt. Therefore it was necessary to use more precise techniques, such as XRD and ICP, for studying the e-waste sample. Figure 2 shows the XRD pattern obtained for the contained metals in the e-waste sample. The most intense peaks correspond to the interest phases of Pt, Ag and Au, in addition to Cu, Zn, Ni and Sn. From this XRD pattern the concentrations of all metallic phases were obtained and they are shown in Table 2. The weight percentage concentrations of Ag, Au and Pt are 11.1%, 6.6% and 6.8%, respectively. Besides, concentrations of Cu, Ni, Zn and Sn with 18%, 19%, 19.7% and 18.8% respectively, were found.

Table 2 Metal e-waste estimated concentrations by DRX

Pattern Phase Weight Percentage % 96-901-3053 96-210-4030 96-901-3036 96-900-8571 96-901-3016 96-901-1600 96-901-8571

Ag Pt Au Sn Cu Zn Ni

11.1 6.8 6.6 18.8 18

19.7 19

The differences between SEM and DRX in the mass percentage of Cu, can be attributed, the technique nature. SEM is a semicuantitative analysis, just a scanning of the sample. While DRX, takes a view of the phases angles contained in the sample. So that it is necessary, to use a more precise technique like ICP, that reveals, all phases content.

632


Figure 2 E-waste sample diffract pattern obtained by DRX.

Table 3 shows concentrations obtained by the ICP technique, where the weight percentage content of Ag is 0.05%, Au is 0.04 % and Pt is 0.0043%. It is important to mention, that most metals contained in e-waste, are present as solders or recovered metal parts. Differences between these results and those presented in Table 1 and 2, can be attributed; to the sample pretreatment. While ICP can reveal all metals, because the acid digestion, X-Ray diffraction and SEM-EDS don´t. These results (table 3) demonstrate that the e-waste are a potential source of precious metals, because of the amount in the sample in comparison to the mining usual concentration, which usually have a smaller percentage of Au, Ag and Pt of 0.000567, 0.01 and 0.0004% respectively.

Table 3 E-waste sample concentrations obtained by ICP.

Element ppm Weight percentage % Cu Ni Zn Ag Au Sn Pt

18324.00 168.82 155.52

9.82 8.40 99.66 0.80

97.64 0.90 0.83 0.05 0.04 0.53

0.0043 Total 100

The results of XRD and ICP verify the presence of significant amounts of Ag, Au, Pt, Cu, Ni, Zn and Sn metals. To carry out the selective electrochemical leaching of a multielemental metallic sample it is necessary to know the potential ranges in which metals are leached. It is therefore compulsory to carry out a thermodynamic study by constructing Pourbaix diagrams that provide information on

633


the potential of the oxidation processes of each metal. However, it is essential to consider this study as an approximation to the real system, because it does not take into account the nature of electrodes and interactions between all metallic elements present. Thermodynamic study Figure 4 (a, b, c, d, e, f, g) shows the Pourbaix diagrams obtained for Ag, Au, Pt, Cu, Ni, Zn and Sn with 9.1x10-5M, 4.2x10-5M, 4.1x10-6M, 2.88x10-1M, 2.86x10-3M, 2.4x10-4M, and 8.39x10-3M concentrations respectively, whereas a concentration of 10% HNO3 and pH 1.03 electrolyte is used. Figure 4a, shows that the formation of Ag+ ionic species and AgO2 oxides is favored in the conditions tested. The Ag+ ion species is favored in a range of electrochemical potential imposed between 0.55V to 1.5V vs SCE at pH 1.03. Moreover, it is observed that the leaching of the ionic species of Ag+ can be affected by the oxygen evolution reaction from the electrochemical potential of 1.17V. Figure 4b shows that Gold produces only one ionic specie, Au+3, which predominates in a range of electrochemical potential imposed between 1.45V and 2.0V vs SCE at pH 1.03. Furthermore, it is noted that production of Au+3 is always coupled with oxygen evolution; because it is presented to less anodic potentials (1.17V) respect to the working pH. Figure 4c shows that the production of oxidized Pt species is favored; PtO, PtO2, throughout the pH range, without the production of platinum ionic species.

In Figure 4d the presence of ionic species, Cu+2 and oxidized copper, Cu2O and CuO, are observed. The production of the ionic species Cu+2 is favored in the range of electrochemical imposed potential between 0.4V and 2.0V vs SCE at pH 1.03 and whose production is carried out, coupled to the oxygen evolution reaction from 1.17 V vs SCE. In Figure 4e, the ionic species of Nickel, Ni+2, oxidized, NiO, and hydroxylated, Ni(OH)3, are observed. The production of the ionic species, Ni+2, is favored in the range of electrochemical potential from -0.3V to 2.0V vs SCE. In addition there is the coupled reaction of oxygen evolution from 1.17V during leaching of nickel.

In Figure 4f, the ionic species of Zinc, Zn+2, and oxidized ZnO, are observed. Production of the ionic species Zn+2 is carried out at electrochemical potentials between -0.7V to 2.0V vs SCE. In addition, the oxygen evolution reaction, observed from 1.17V, affects leaching process of zinc Zn+2 species.

Figure 4g shows that the production of ionic species Sn+2 and oxide SnO2 is possible; however, the ionic species Sn+2 are favored in a small range of electrochemical potential of -0.1V to -0.25V vs SCE.

634


(a) (b)

(c) (d)

(e) (f)

635


Figure 4 Pourbaix diagrams for a) Ag , b) Au, c) Pt, d) Cu , e) Ni, f) Zn and g) Sn considering

pH 1.03 nitric acid concentration.

Taking into account the above, redox reactions under standard conditions for ionic metal species, which are expected to carry out under the conditions of this work are:

Cu2+ + 2e− Cuo Eo = 0.34 (1)

Ni2+ + 2e− Nio Eo = − 0.250 (2)

Zn2+ + 2e− Zno Eo = − 0.73 (3)

Sn2+ + 2e− Sno Eo = − 0.36 (4)

Au3+ + 3e− Auo Eo = 1.49 (5)

Ag+ + e− Ago Eo = 0.799 (6)

Pt2+ + 2e− Pto Eo = 1.2 (7)

It is worth mentioning that these equilibriums are affected by the specific conditions of the real system, and there can be deviations in the values of potential to which the leaching process is held. Therefore, the thermodynamic results indicate that it is possible the Ag+ and Au+3ionic species existence, without platinum; under working conditions. However, these results do not take into account other important factors such as the electrodes nature or interferences in the equilibrium state due to the rest metals interactions.

Conclusions

The characteristics of the metal sample evaluated were determined by verifying the amount of each metal, showing that the e-waste are a viable source for the recovery of Ag, Au, Pt, Cu, Ni, Zn and Sn.

(g)

636


The thermodynamic study indicated that it is possible to obtain the ionic species of Ag, Au, Cu, Ni and Zn metal at an interval of electrochemical potentials of 1.45V to 2V at a pH of 1.03. It is also noted that the tin ion species are produced in an interval of electrochemical potential of -0.1V to -0.25V vs. SCE. Conversely, the formation of platinum ionic species in this potential range and in this medium is not favored. So also it can be concluded that the HNO3 is a suitable medium for the leaching of most metals in e-waste.

References

1. Jadhov, U. (2012). Recovery of precious metals from industrial waste. Journal of achievements in materials and manufacturing engineering , 4 (2), 159-167.

2. Escutia, L. (2003). Lixiviación de Ag a partir de concentrados sulfurados con thiourea electrodo-oxidada. Tesis para obtener el grado de Maestro en Ciencias . Ciudad de México: UAM Iztapalapa.

3. Newton, J. (2002). An introduction to Metallurgy ( Segunda edición ed.).

Documents

Proceedings of a symposium sponsored by · 629 JWBT1826-Characterization_of_Minerals_Metals_and_Materials_2016.indd21 December 2015 11:51 AM 629 SPECIATION AND CHARACTERIZATION OF